What is a cat’s menstruation like?

Cats do not menstruate. Their physiology differs from dogs; they ovulate only when stimulated by a male during mating, so a female in heat shows no bloody discharge, only a little clear mucus. If you see vaginal bleeding, it may be mating injury or uterine/ovarian disease; see a vet.

During heat, cats also yowl, raise their rump, become unusually clingy, irritable, and may run away; comfort the cat and keep doors and windows closed.